MicroRNAs in Breast Cancer (Editor: Marc Lacroix)

MicroRNAs, or miRNAs, are a recently discovered class of small
regulatory RNAs that influence the stability and translational
efficiency of target messenger RNAs (mRNAs). Alterations in miRNA
expression are associated with an increasing number of biological
processes, including breast cancer. Some miRNAs are up-regulated in
breast tumors, such as miR-21, miR-155, miR-373, and miR-520c, and
appear as putative oncogenes. Other miRNAs are down-regulated, such as
miR-126, and miR-145, and members of the let-7 family; functional
studies support their tumor suppressor nature. miRNAs associated with
estrogen receptor expression and function, such as miR-18a, miR-22,
miR-181, miR-206, miR-221 and miR-222, or with HER2/neu, such as
miR-125, have also been identified. Other miRNAs, such as miR-210 and
miR-421 have been linked to hypoxia and drug resistance, respectively.
Of peculiar interest are miRNAs (miR-200 family members, miR-205)
involved in epithelial-mesenchymal transition (EMT), a process that is
proposed to play an important role in cancer cell metastasis. The
study of miRNAs is a rapidly developing field that could considerably
change our vision of breast cancer biology.
This book offers an insight into our current knowledge of human
miRNAs, with a specific interest for breast cancer. What are exactly
miRNAs, how are they found, how are their target mRNAs identified,
which miRNAs are of importance in breast cancer, notably from a
clinical point of view ? Elements of response to these questions are
brought here.